why?
It doesnt matter how many calories you burned running, cycling, walking, or weight training, as long as you do it your fine. THe only thing that matter is that you atleast fix in the activity multiplier into your calories, and thats a broad multiplication

"Love like your life depends on it, live like love is the only thing worth living for"
"Train because you love to, train because you love yourself"

400...WOW..can you do that much? at once?? I'm sure there are better ways to spend your time doing cardio if you're just looking to burn cals.
As far as the reps to make the "six-pack" , I would rather do weighted ab exercises (and a lot less of them) to get that look than 400 of anything non-weighted.
YMMV

400...WOW..can you do that much? at once?? I'm sure there are better ways to spend your time doing cardio if you're just looking to burn cals.
As far as the reps to make the "six-pack" , I would rather do weighted ab exercises (and a lot less of them) to get that look than 400 of anything non-weighted.
YMMV

Definitely do less and do something that is more difficult so that you are reaching close to failure and not just stopping because you reached a number.

You're building endurance though I suppose, but I question your form on them if you can do 400. I can do a lot if I just do them rapidly, but if I do them properly, exhale forcefully as I contract to get a full hard contraction of the abs at the top, then I can't do a lot.

I wondered into this topic using google.
And even though this is an old post, I wonder why it is so hard for people to answer this simple question, than to critique the original posters method without understanding the reason of his question?

I was trying to find out an estimate of how many calories I burn doing different activities, like swimming, weight training, ab training, rock climbing, basketball, football, tennis, and so on. This is so I can get a baseline figure of how many calories I am taking in vs. how many calories I am expending.

You can search for it. Im sure somewhere in bb.com, or lookin google, it has the # of cals u burn doin crunches. But i do not recommend u count those. I mean, if you are trying to lose weight, burn 500 calories a day, every day, 7 days a week, and you lose 1 lb. Eat 500 calories less a day, every day, 7 days a week, you will lose another 1 lb, which will be a total of 2 lbs/week you will lose.

Whenever i want to lose 1 lb a week from cardio, i just go run for 500 calories on the treadmil. Sometimes i play basketball, and i DO NOT count those calories, because it will eventually show up on the scale, that i have lost more. Just do not worry about those calories.

April 2007 - Age 16 - 261lbs
October 2009 - Age 19 - 180lbs
Now - October 2010 - Age 20 - ~196.6lbs

I agree with the others. Your composition of your abdominal muscles is no different than those found in the rest of your body, and I doubt you're doing 400 reps of bench or squats. Do weighted ab exercises in the 8-12 rep range and do some cardio if you want to burn calories.